A warming climate or a hoax

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Friday, November 10, 2006
Sen. James Inhofe, R-Okla., chairman of the Environment and Public Works Committee, has said the idea that humans are causing global warming is the "greatest hoax ever perpetrated on the American people." Here are some of his key assertions:

_ Temperatures are rising as part of a natural warming trend.

His view: Inhofe says the world is in the midst of a natural warming period that started in 1850 as we came out of a 400-year cold spell known as the Little Ice Age. He cites studies suggesting that rising temperatures might be linked to variations in the amount of energy emitted by the sun.

Counter-argument: Most scientists say natural variability is a factor in climate change, but it can't explain the rapid warming in recent decades. The National Academy of Sciences said recently the "Earth's warming was not due to changes in the sun." The academy, the United Nations Intergovernmental Panel on Climate Change, the American Meteorological Society, the American Geophysical Union and the American Association for the Advancement of Science have all concluded that increased greenhouse gas concentrations resulting from human activities are the likely cause of rising temperatures. The Bush administration, in a 2002 U.S. Climate Action Report by the EPA, said global warming was "likely due mostly to human activities," but said natural variability could play "some significant part."

_ Temperatures actually declined between 1940 and the 1970s, even as carbon dioxide levels rose.

His view: Inhofe says this fact shows that human activities, especially the burning of fossil fuels, can't be blamed for global warming. The senator notes that media stories in the mid-1970s warned of the negative effects of a global cooling trend, including crop failure.

Counter-argument: Mean temperatures in the Northern Hemisphere cooled somewhat during that period, after having risen steadily since the mid-1800s. Many climate scientists say it's more significant to look at the long-term pattern of warming across the globe. Records show that surface temperatures have risen by 1.4 degrees since the early 20th century, including a 0.9 degree increase since 1978.

_ Computer models that predict drastic temperature increases and sea level rises are unreliable.

His view: Inhofe, citing uncertainties in modeling, said last month: "The science is simply not there to place so much faith in scary computer model scenarios which extrapolate the current and projected buildup of greenhouse gases in the atmosphere and conclude that the planet faces certain doom."

Counter-argument: Scientists agree that computer models can't predict precisely what the effects of climate change will be, mostly because of the many variables that affect projections, such as population and economic growth, and energy usage. But the National Academy of Sciences noted that computer model predictions of temperature changes in the 20th century have closely matched observed temperature changes.

Sources: National Academy of Sciences; Senate Environment and Public Works Committee, San Francisco Chronicle research.